1. Field of the Invention
The present invention relates to a thermally responsive valve for an engine of a motor vehicle and more particularly, to an improved thermally responsive valve which includes an upper housing having an inlet port, an outlet port, a cylindrical chamber, and a main chamber; a lower housing having a longitudinally elongated aperture, a thermal transmitting cover and a thermal expansion member such as wax; and a movable shaft piston disposed within the main chamber of the upper housing and the longitudinally elongated aperture of the lower housing. The movable shaft piston contacts the thermal expansion member at one end and has a compression spring at its other end, whereby upon expansion or shrinkage of the thermal expansion member in response to engine body temperature, the movable shaft piston moves upward or downward and causes the cylindrical chamber to close or reopen by means of the top portion blocking or re-establishing communication between the inlet port and the outlet port of the upper housing.
2. Description of the Prior Art
Various types of thermally responsive valves for detecting the temperature of an engine of motor vehicles are known. Such thermally responsive valves are shown in U.S. Pat. No. 3,841,551 to Ota, U.S. Pat. No. 3,960,321 to Steele, U.S. Pat. No. 4,000,849 to Steele et al, U.S. Pat. No. 4,036,433 to Wagner et al, U.S. Pat. No. 4,128,203 to Malthy, U.S. Pat. No. 4,133,349 to Stripling, U.S. Pat. No. 4,165,035 to Maltby, U.S. Pat. No. 4,185,663 to Stripling, U.S. Pat. No. 4,239,152 to Kitamura et al, U.S. Pat. No. 4,285,467 to Maltby, U.S. Pat. No. 4,335,690 to Hosokawa et al, U.S. Pat. No. 4,375,873 to Enomoto et al, and U.S. Pat. No. 4,386,732 to Satomoto. However, these thermally responsive valves can be inconvenient or unreliable. Also, most of such thermally responsive valves are bimetallic element assemblies. Such bimetallic element assemblies suffer from a number of disadvantages such as, for example, (a) it is very difficult for the on/off system of such assemblies to actuate suddenly, since after the temperature increases to a predetermined temperature, such assemblies tend to return to the original position, (b) it is difficult for an on/off system of such assemblies to be inefficiently completed, and (c) since the bimetallic element material of such assemblies is not so good for detecting the heat, it has to be replaced after a short time period.